1. Field of the Invention
This invention relates to a recording head to be employed for a liquid jet recording method, in which recording is effected by formation of flying droplets.
2. Description of the Prior Art
Non-impact recording methods have recently drawn attention of all concerned in that noises generated at the time of the recording are low or negligible. Of these non-impact recording methods, the so-called "ink jet recording methods (or liquid ejecting recording methods)", which is capable of performing high speed recording, and of recording an image on plain paper without requiring any particular treatment of image fixing, is considered to be extremely useful recording method. Heretofore, various systems for the ink jet recording method have been devised, some of which have already been commercialized with necessary improvements having been incorporated, and others of which are still under way for their practical use.
Such liquid ejecting recording method is to effect the image recording by causing droplets of a recording liquid which is usually called "ink" to fly toward an image recording member and to adhere thereon, which method is largely classified into several systems depending on the method of generating the droplets of this recording liquid and the method of controlling the flying direction of the droplets thus generated.
Of various systems for the liquid ejecting recording method, those as described in U.S. Pat. Nos. 3,683,212, 3,946,398, and so forth, for example, are called the "drop-on-demand" recording methods which effect the image recording by causing the droplets to discharge and fly from a discharging orifice, and causing the droplets to adhere onto the image recording member surface. This drop-on-demand recording method has recently drawn a particular attention of all concerned for the reason that since only droplets necessary for the recording are discharged, no particular means is required for recovery or treatment of the discharged liquid which are not necessary for the recording with the consequence that the recording apparatus per se can be made in a simple construction and small size, the flying direction of the droplets discharged from the orifice needs not be controlled, polychromatic recording can be effected easily, and others.
Besides the abovementioned liquid jet recording method, laid-open Japanese patent application No. 54-59936 (corresponding to DOLS 2843064 and U.S. Ser. No. 948,236) discloses an entirely different liquid jet recording method in its droplets forming principle. This liquid jet recording method is not only applicable very effectively to the abovementioned drop-on-demand recording method, but also capable of readily embodying the recording head in the full line type, high density multi-orifice construction, hence it has such characteristic that an image of high image resolution and quality can be obtained at high speed.
The recording heads for use in these liquid jet recording methods are so designed in construction, and so provided with necessary devices, that each of the recording methods may exhibit its characteristics to the maximum possible extent, although they are common in their fundamental construction to be mentioned in the following.
That is, the liquid jet recording head to be used in these recording methods basically has a liquid discharging portion constructed with an orifice side end part having at its tip end an orifice for discharging liquid, an energy acting zone which is communicatively connected with the orifice and where energy acts on the liquid to form flying droplets, and an inlet side end part connected with the energy acting zone and having an inlet port to introduce the liquid into the energy acting zone.
The energy acting zone is such one that, in the case of the recording method as disclosed in U.S. Pat. Nos. 3,683,212 and 3,946,398, for example, an electro-mechanical transducer such as a piezoelectric element, etc. is provided in a mechanically coupled relationship, wherein, by pressure energy (pressure wave) generated by an input recording signal into the electro-mechanical transducer, the droplets are discharged and flown to effect the recording. According to one of the recording methods as disclosed in the laid-open Japanese patent application No. 54-59936, an electro-thermal transducer is provided at the energy acting zone, and discharging and flying of the droplets for recording are effected by heat energy to be generated by application of an input recording signal to the transducer. Further, according to another recording method as disclosed in this laid-open patent application No. 54-59936, no particular means is provided at the energy acting zone, but electromagnetic wave energy such as laser, etc. is irradiated onto the energy acting zone to cause it to be absorbed in the liquid at this energy acting zone to thereby generate heat, by the heat generating action of which the droplets are discharged and flown for recording.
According to the recording methods as disclosed in this laid-open patent application No. 54-59936, the heat energy is caused to act on the liquid in the manner as mentioned above to obtain the driving force for the droplets discharging. In more detail, the liquid which has been subjected to the action of the heat energy brings about the state change accompanying abrupt increase and decrease in the liquid volume, i.e., generation of bubbles and decrease in the volume of the bubbles as generated, and, by the force of action based on the state change, droplets are discharged and flown from the orifice at the tip end of the orifice side end part, and adhere onto an image recording member for recording.
Thus, the liquid jet recording method described in the foregoing obtains the driving force for the droplets discharge by causing the pressure energy or heat energy to act on the liquid at the energy acting zone. Accordingly, it is necessary that such energy act on the liquid in a manner to be efficiently spent for the droplets discharge.
In the case of continuous recording, it is necessary that formation of the flying droplets be repeatedly done in exact response to the recording signal. In particular, in the case of high speed recording, this repetition of the droplets formation should be done faithfully and quickly in accordance with the recording signal to be imparted to the energy acting zone.
Furthermore, in order to improve the quality of the recorded image and to make it possible to perform the recording at high speed, it is necessary that the droplets discharging direction be stabilized, satellite droplets be prevented from occurring, the repeated droplets discharging be done stably and continuously over a long period of time, the droplets forming frequency (number of droplets to be formed per unit time=frequency of the droplets formation per unit time) be improved, and various other improvements in the characteristics for the stabilized droplets formation be attempted.
Unfortunately, however, all these requirements as mentioned above cannot be said to have been solved satisfactorily in the conventional methods.